After a successful amateur career, which culminated in his Olympic gold medal win, Spinks went undefeated in his first 31 professional fights, beating Dwight Muhammad Qawi, Eddie Mustafa Muhammad, Marvin Johnson and Eddie Davis en route to becoming the undisputed light heavyweight champion.

The International Boxing Research Organization and BoxRec rank Spinks among the 10 greatest light heavyweights of all time.

[citation needed] He rebounded to take the 1976 National Golden Gloves Middleweight championship with a three-round victory over Lamont Kirkland in Miami, Florida, and that same year captured the United States Olympic Trials Middleweight Championship by defeating Keith Broom in Cincinnati, Ohio.

[11] Gold at the XXI Summer Olympics (165 lbs), Montreal, Canada, July 1976: Spinks finished his amateur career with a record of 93 wins (35 knockouts,) 7 losses.

[12] With the Olympics behind him, Spinks returned to work at a chemical factory in St. Louis, Missouri, "scrubbing floors and cleaning toilets," as one source tells it.

[8][14][15] Spinks then turned professional with a win over Eddie Benson, knocking him out in one round on April 17, 1977, in Las Vegas.

After four more wins, Spinks finished '77 with the first fight that began a gradual ascent in opposition quality: an eight-round decision over Gary Summerhays, a popular young boxer of the time.

1979 saw Spinks get less than three minutes of boxing action inside a ring, with his only fight ending in a first round knockout of Marc Hans, but in 1980, Spinks took his ascent towards the top to another level, when he beat future IBF super-middleweight champion Murray Sutherland, David Conteh, and fringe contenders Ramon Ronquillo and Alvaro Yaqui Lopez (who challenged for a world title four times).

By 1981, Spinks was already a top ranked contender, and after beating former and future world light-heavyweight champion Marvin Johnson by a knockout in four rounds, the WBA made Spinks their number one challenger, and so, on July 18 of that year, he met WBA light-heavyweight champion Eddie Mustafa Muhammad, once again in Las Vegas.

Tragedy struck his life, however, when in January 1983, his 24-year-old wife, Sandy Massey, died in a car crash, leaving Spinks the single parent of his two-year-old daughter, Michelle.

On March 18, two months after his wife's death, Spinks and Qawi met in a boxing ring for the undisputed light heavyweight championship.

In 1985, Spinks beat David Sears and Jim McDonald, both by knockout, in title defenses, before challenging Larry Holmes for the IBF and lineal heavyweight championship.

The Ring Magazine in 2002 ranked Spinks as the third greatest light-heavyweight of all time, behind Ezzard Charles and Archie Moore, but ahead of Tommy Loughran, Bob Foster, Harold Johnson, Maxie Rosenbloom and Billy Conn.

"[22] Spinks was once believed to be one of the few top fighters who left the sport of boxing with both a decent amount of money and being seemingly unharmed, free of permanent injuries.

Aside from a rare event honoring him and occasionally attending fights, Spinks has largely remained off the boxing scene and out of the public eye.

"Spinks had to invade his pension and retirement funds and incur significant taxes and penalties in order to meet these obligations," the boxer's lawyers added in the filings.